It’s an unusual beauty treatment meant to rejuvenate the skin on your foot, but a medical professional is warning the public to steer away from “fish pedicures” after a woman lost her toenails from the procedure.

According to a case report published by the patient’s doctor in JAMA Dermatology, the woman’s toenails stopped growing and started falling off months after getting a fish pedicure in New York.

A fish pedicure involves soaking your feet in a tub of warm water while little toothless carp, called Garra rufa, peck away at the dead skin on the surface of your feet. Garra rufa, also known as “doctor fish,” are freshwater fish that are native to waters from the Persian Gulf to the eastern Mediterranean and have long been revered for their perceived healing power.

The woman, who is in her 20s, said after the fish pedicure, most of her toenails on both feet stopped growing and began to fall off, a condition known as onychomadesis.

Six months later, she went to a dermatologist, who ruled out any other causes of onychomadesis, such as a family history of nail disorder, medical problems or previous trauma. The dermatologist said it was most likely linked to the fish pedicure.

Fish pedicures are said to leave feet smoother and smelling fresher, however, these claims are “unfounded,” according to Lipner, adding there are many risks associated with it.

“First, tubs and fish cannot be adequately sanitized between people, and the same fish are typically reused for successive persons,” Lipner said. “Thus, there are concerns of transmitting infections between people undergoing these pedicures.”

And even if spa owners can properly sanitize the fish and tubs, research shows disease-causing bacteria can be readily found in both the tubs and fish used in these spas, she added.

“While the mechanism of action is not entirely clear, it is likely due to the fish traumatizing the nail matrix,” she told Gizmodo.

“I do not recommend fish pedicures for any medical or aesthetic purpose,” Lipner said. “In addition to onychomadesis, there are also serious infections associated with fish pedicures.”

Here in Canada, fish pedicures are banned in some provinces, such as Ontario, Manitoba and Alberta due to health risks. In 2011, the Vancouver Island Health Authority also banned it, saying that there were bacterial risks because the fish could not be sterilized.